1. Field of the Invention
The present invention relates to a knock detection device for an internal combustion engine and, more particularly, to a knock detection device capable of rapidly and accurately detecting heavy knock.
2. Description of the Related Art
When applying a newly developed automotive internal combustion engine to an actual automobile, work known as conformance work becomes necessary in order to determine optimum values of parameters (fuel injection amount, ignition timing, valve open/close timing, etc.) to be programmed into an engine control computer, by actually running the internal combustion engine under the various driving conditions that the engine is expected to encounter in actual driving situations.
If all of the conformance work is to be performed manually, many hours (man-hours) will be required; in view of this, the following method is proposed to automate the work for computing the knock detection threshold.
FIG. 1 is a functional diagram of a test setup for implementing the prior art knock detection method. The cylinders in the internal combustion engine 10 are provided with pressure sensors 101 to 104 (in the case of a four-cylinder engine) for measuring the internal pressure of the corresponding cylinder.
The cylinder pressures measured by the pressure sensors 101 to 104 are collected into a high-speed data logger 12 via an amplifier circuit 11. The high-speed data logger 12 also collects data on the crankshaft angle of the internal engine.
The data collected by the data logger 12 is transferred to a cylinder pressure analyzing personal computer 13 which computes the threshold value for knock detection.
Here, to determine an optimum threshold value, the cylinder pressures must be detected, for example, for about 10 seconds (several hundred cycles), and the results must be processed.
There has also been proposed a method that determines, based on cylinder pressure and load information, whether knock has or has not occurred (refer, for example, to Japanese Unexamined Patent Publication No. 2001-32744).
If the magnitude of the knock is large (a heavy knocking condition), a knock suppression measure involving, for example, reducing the spark advance angle, or retarding the intake valve open/close timing, must be applied immediately since such knock can lead to mechanical damage to the internal combustion engine; however, with the prior art knock detection method which takes about 10 seconds to determine the threshold value, if heavy knock occurs before the threshold value is determined, mechanical damage to the internal combustion engine is unavoidable.